The studies reported by this grant have investigated the development of a specific antibody to a pancreatic oncofetal protein (POP). Antisera to POP were raised in New Zealand rabbits by immunization with extracts of human fetal pancreas (8-16 weeks of gestation) and pancreatic cancer tumors. The antisera produced against fetal pancreas were made POP-specific following exhaustive absorptions with lyophilized human serum, adult human liver and adult human pancreas. Immunodiffusion experiments of the absorbed antiserum with fetal liver and fetal pancreas showed a partial antigenic identity of POP and fetal liver. This incomplete identity reaction, as indicated by spur formation, suggests that POP is not identical with liver oncofetal protein (?alpha-fetoprotein) but it may be closely related to it. POP was found to have an alpha 2 migration on immunoelectrophoresis. This type of mobility enabled us to develop a counterimmunoelectrophoresis which is expected to increase the sensitivity of the assay system significantly. Fractionation of pooled human fetal pancreases has shown the following: 1) Following centrifugation at 12000xg for 30 minutes POP can be detected in the soluble fraction of pancreatic protein but not in the particulate matter. 2) POP was precipitated with saturated ammonium sulfate at concentrations between 35% and 40%. 3) Ion exchange chromatography on a DEAE-cellulose showed that POP could be separated from several other proteins and was eluted only following the application of a 0.1-1.0 M NaCl gradient in the starting buffer. 4) Polyacrylamide gel electrophoresis revealed significant purification of the POP but even the DEAE fraction resolved in several protein bands.